Extensive research indicates that cyclic AMP regulates the motility and metabolic activity of sperm. However, the factors which alter cyclic AMP concentration in sperm are poorly understood. The overall objective of this project is to determine how cyclic AMP concentration in sperm is regulated. The enzymes, adenylate cyclase and phosphodiesterase, which are responsible for cAMP metabolism, will be studied using guinea pig and bull sperm. Cell fractionization techniques will be used to determine the subcellular location of these enzymes and separate different enzyme forms. The enzymatic and regulatory properties of adenylate cyclase and phosphodiesterase, will be determined, particularly with respect to divalent metal ions and other potential effectors. In vitro capacitation techniques for guinea pig sperm will be used to detect alterations in enzyme activity during capacitation and to identify and characterize factors which regulate enzyme activity and cyclic AMP concentration.